Steel is widely used in various fields of life, architecture, bridges, scientific research, etc. The quality of steel is subject to a variety of mechanical tests to ensure their strength, elastic constants and other material properties. And their performance in various practical conditions and environments. Tensile testing is one of them.

What is tensile test

Tensile test is a test method for determining the properties of a material under axial tensile load. The data obtained from the tensile test can determine the material's elastic limit, elongation, elastic modulus, proportional limit, area reduction, tensile strength, yield point, yield strength, and other tensile properties. The tensile test of steel meets the ASTM E-8 standard.

There are 4 stages in the tensile process:

1, the elastic stage (the stress and strain ratio increases, the unloading load can be restored)

2, the yield phase (the increase in strain is greater than the increase in stress, began to produce plastic deformation, the lower stress is the yield point)

Step 1. Prepare the test piece. The ruler is used to scribe a circle in the original gauge range (or punch a small punch with a small steel) to divide the gauge length into ten equal lengths. Use a vernier caliper to measure the diameter at two ends of the specimen's original gauge length and in the middle at two mutually perpendicular directions. Take the arithmetic mean value as the diameter of the section at that location, and then use the minimum value of the three section diameters to calculate The original section area A of the test piece.

Step 2. Adjust stell tensile test machine. Calculate the maximum load of the specimen based on the tensile strength σb of the steel and the original cross-sectional area, configure the corresponding pendulum, and select the appropriate force measurement dial. Start the tester and raise the worktable by about 10mm to eliminate the influence of the worktable system's own weight. Adjust the active pointer to the zero point, move the pointer and the active pointer closer, and adjust the automatic drawing device.

Step 3. Set up the specimen. First clamp the test piece in the upper clamp, then move the lower clamp to the proper clamping position, and finally clamp the lower end of the test piece.

Step 4. Check and test run. Check the above steps to complete the situation. Start the tester, preload a small amount of load (load corresponding to the stress can not exceed the material limit of the ratio), and then unloaded to zero to check whether the test machine is working properly.

Step 5. Test. Turn on the tester and slowly and evenly load. Observe the rotation of the force hand and the drawing of the drawing device. Pay attention to capture the yield load value, record it to calculate the stress value σS at the yield point, pay attention to observe the slip phenomenon in the yield phase. After the yield phase, the loading speed can be faster. When the maximum value is to be reached, observe the "necking" phenomenon. Stop the test piece immediately after the break and record the maximum load value.

Step 6. Remove the test piece and recording paper.

Tensile test related data

Tensile test fixtures

The tensile clamp itself is a locking mechanism. There is no fixed pattern in the structure. According to different specimens and test force size, there is a great difference in structure. The test specimen with large test force generally adopts inclined clamping structure. As the test force increases, the clamping force increases. Shoulder specimens using suspension structure.

Related test machines

Hydraulic universal tensile testing machine can achieve closed-loop control of various modes such as constant force, constant stress, constant deformation and constant speed, and complete the tensile, compression, bending and shear tests of metal materials and non-metal materials. Microcomputer-controlled electro-hydraulic servo universal testing machine adopts the under-cylinder under the fuel tank, equipped with the electro-hydraulic servo oil source and the independent low-noise clamping oil source imported from the Italian oil pump motor group and servo valve. Full digital program-controlled amplifier with intelligent control system setting expert system.